Obturating firing pin



Aug. 23, 1949. s. WEISS ET AL OBTURATING FIRING PIN Filed July 2, 1,947

EDGAR [LED 5 EH'TS Patented Aug. 23, 1949 OBTURATING; FIRING PIN ,Saul Weiss, Washington, D. 0., and Edgar C. Roberts, Arlington, Va.

Application July 2, 1947, Serial No. 758,698

7 Claims. (eras-27 '(Granted under the act of March 3, 1883, as

The invention described herein may be manufactured and used by or for the Government for governmental purposes-without the payment to us of any royalty thereon.

Our invention relates to firing pins for guns and more particularly to firing pins which are movable to fire a gun and which incorporate structure for preventing the passage of propellent gases through thepassage in which the pin operates.

While our invention is particularly adapted for use in firearms such as trench mortars or cannon which use caseless cartridges orseparate loading ammunition wherein the propellant is not contained in the usual metallic cartridge case, it may be used with all types of firearms which include a movable firing pin.

The usual firing pin is carried by a bolt or other mounting means and generally is propelled for firing by a Spring. In the firing position the pin is usually extended through a hole or passage through the forward end wall of the bolt; The pin does not have a sealing fit in the passage, and, as a result, corrosive gases of the propellant escape'through the passage aforesaid and have a deleterious effect on the firing pin spring and other parts of the bolt as well as on related working parts of the firing mechanism.

We are aware of Patent .No. 1,345,565, issued July 6, 1920, to J. T. Thompson, for a firing pin of this general type. However, our invention goes well beyond the showing and teaching of this patent.

With the foregoing in view, it is an object of our invention to provide improved .means for preventing the passage of propellent gases past the firing pin, irrespective of the position of the pin.

Further objects are to provide such an improvement by utilizing the gas pressures created by the explosion of the propellant to seal at least partially, the firing pin in its passage; to provide expansion chambers associated with the pin to trap gases attempting to seep past the pin; and to provide means for scraping residue from the walls of the pin and/or pin passage, which means is operative by the normal movement of the pin in use.

Other objects and advantages reside in the particular structure of our invention, combination and arrangement of the several parts thereof and in the particular method or mode of operation, all of which will be readily apparent to those skilled in the art'upon reference to the attached drawing and appended specification wherein the invention is shown, described and claimed.

amended April 30, 1928; 370 0. G. 757) fit in the bore 3|.

In the drawing:

Figure 1 is a fragmentary, longitudinal, sectional view through the breech of a firearm showing our improved firing pin in its retracted posiion;

Figure 2 is a view like Figure 1 but showing the pin in the advanced position; and

Figure 3 is an enlarged and exaggerated fragmentary sectional view of a detail.

Referring specificially to the drawing, wherein like reference characters have been used throughout to designate like parts, it designates any suitable firearm. In the embodiment illustrated, the invention is shown applied to a muzzle loading weapon of the trench mortar type. However, it is understood that the invention is applicable to other weapons of both the breech and muzzle loading type which use firing pins.

The floor ll of the bore of the mortar I0 may be formed with a recess l2 therein in which a bushing l4 may be secured by any suitable means [3. The'base of the bushing l4 and floor of the recess I2 are provided with opposed and complementary recesses in which is seated an annular collar l5 the inner periphery of which lies radially and concentrically inward of the periphery of the forward end of a rearwardly extending passage [6 to form an annular shoulder [1. The passage l6 comprises a reduced extension of the recess l2. The'forward end of a cylindrical collar [8 for a hammer or striker 22 seats against the shoulder II. The rearward end of the collar I8 is inwardly flanged at 20 to confine the flanged head 2i of an elongated hammer or striker 22. The rearward surface of the flange 20 of the collar [8 seats the forward end of the hammer spring l9 and normally maintains collar 58 in contact with the flanged head 2| of the hammer for reciprocal movement with the hammer. The hammer 22 is reciprocably mounted in the passage [6 and is urged forwardly by the spring IS. The rearward end of the spring I9 is seated in the passage I 6 by any suitable means (not shown).

The forward face of the bushing I4 is formed with a circular axial recess 30. The bushing is formed also with an axial bore 3| which opens into the recess through the floor 32 thereof. A firing pin, generally indicated by 33, is reciprocably mounted in the recess 30 and bore 3 I.

The firing pin 33, comprises a cup shaped, piston-like head 34 which has a close sliding fit in the recess 30 and a stem 35 which has a like The rear end of stem 35 is formed with a flanged head 36 which retains a washer 31 on the stem. A firing pin return spring When released by any suitable by the seat I? (Fig. 1) at which point the ham-.v

mer has contacted the head 35 of the firing pin. Thereafter, the inertia of the hammer causes it to continue forwardly carrying the firing 'pin 33 with it (Fig. 2) against the relatively weak pressure of retracting spring 38 of the firing pin. 7

As the detonator (not shown) of the-projectile is seated flush against the forward face of the bushing I l, the piece is ifired when the firing pin 33 reaches the Figure 2 position. .After firing the expansion of the propellent gases returns th firing pin and hammer to the Figure 1 position and the retracting spring 38 is able to maintain those parts in that position as the engagement of collar it.- with seat ll relieves the hammer of any load from hammer spring l9.

At the same time, the expansion of the propellent gases tend to spread the cylindrical wall of the piston-like head 34 of the firing pin and to force such walls into a sealing engagement with the bore 30. The outer periphery of the head 34 is scored in any suitable manner as by one or more annular grooves 40 which have a, triple function. Frst, the provision of the grooves 40 reduces the area of the outer surface of the h-ead34 which is in contact with the walls of the recess 30. Thus, under the pressure of the expanding propellent gases, the lands 4! between the grooves 46 tend to dig into the walls of recess 36 to increase the scaling action. This eifec't' is shown in Figure 3 and has been slightly exaggerated for the sake of'clarity.

Secondly, the grooves 40 act as expansion chambers for any gases which reach them whereby the pressure of the gas is progressivelyreduced the further it penetrates.

Thirdly, the reciprocal action of the firing pin causes the relatively sharp edges of the lands 4! to act as scrapers to scrape any residue of the gases from the walls of the recess 36. In this function the grooves 40 act as receptacles for such residue.

The stem 35 of the firing pin may be similarly scored as by one or more annular grooves 42 which provide lands therebetween. Such grooves and lands perform the second andthird functions of the grooves and lands 4!], 4| as aforesaid.

In addition to the improved sealing achieved by the lands and grooves, the expansion of the propellent gases forces the head 34 of the firing pin against the fioor of the recess 30 whereby is provided an additional safeguard against leakage of gas past the head 34.

In weapons of the trench mortar type, the piece frequently utilizes a stationary firing pin and the projectiles are fired by being dropped thereon through the muzzle of the piece. The weapon shown herein may be fired in this manner by moving the parts to the Figure 2 position and locking the hammer at that point by any suitable means (not shown). When so fired, the sealing means functions in substantially the same way as before except that an additional gas expansion chamber 43 is formed by the space between the head 34 and the floor of the recess 30. Obviously the grooves need not be on the pin but may be on the walls of the recess or on both recess and pin. Nor do we limit ourselves to the precise-form of groove shown,

, While we have shown; and described what is now thought to be the preferred embodiment "of our invention, it is to be understood that the same is susceptible of other forms and expressions. Consequently, we do not limit ourselves to the disclosure herein shown and described except as hereinafter claimed.

We claim:

1-. 'In a gun Having a, firing chamber, a recess opening into said chamber, and a firing pin removably fitted in said recess; said pin having a peripheral surfaceportion thereof adapted to be forced iiftointimate contact with an abutting surface portion of the wall of said recess by the pressure 'ofproiectiie' propellent gases, and atleast one" 'of said surface portions being scored to cooperate with said other surface portion to substantially seal said pin in said recess momentar'ily 'by said gas pressure, there being a reduced 'pasage through the fioor of said recess, an extension of said pin fitted in said passage with surfaceportions thereof abutting surfaceportions of said passage, and one of said last named surf-ace portions'being scored.

-2. The structureof claim -1-, and said first named scored surface being a surface of said pm. M

3. The structure off'claim 2-, and, said last named scored surface "being a surface of said pin extension.

4. In a gun having afiring chamber, a recess opening into said chamber, and a firing pin removably fitted in said recess; said .pin having a plurality of surface portions thereof adapted to be forced into intimate contact with abutting surface portions of said recess by the pressure of projectilepropellent gases, and at least one of's'aid'surface portions of one of said pin and recess being' formed with at least one annular groove 'to cooperate with the abutting surface portion to substantially seal said pin in said recess during'the duration of said gas pressure, there being a reduced passage through the floor of said recess, an extension of said pin closely fitted in said passage, and at least one annular groove formed in one of the abutting surface portions of said-pin extension and passage.

5. The structure of claim 4, and said first named groove being formed in a surface of said pin.

6. The structure of claim 5, and said last hamed surface "being formed in the surface of said pin extension.

'7. ha gun having a'flring chamber, a recess opening into said chamber, and a firing pin removably fitted in said recess; said pin hav-- ing a plurality of surface portions thereof adapt ed'to be forced int'o'lntima'te contact with abutting surface portions of said recess by the pres-- sure of projectile propellent gases, and at least one of said surface portions of one of said pin and recess being formed with at least one an nular roove to cooperate with the abutting sur face portion to'substantiallyseal said pin in said recess during the duration of said gas pressure, a reduced passageth-roiigh thefioor of said recess, an extension of said pin closely 'fittea in said assage, and a plurality of spaced "and "parallel annular grooves formed in the peripheral surface of said pin extension.

SAUL WEISS. EDGAR C. ROBERTS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Reising Aug. 26, 1919 Number Number 

